Piezoelectric voltage source



26, 1969 D. B. PARKINSON 3,463,943

PIEZOELECTRIG VOLTAGE SOURCE Original Filed April 11, 1966 I INVENTCR.

DAVID B. PARKINSON F IG .3

ATTORNEY United States Patent 3,463,943 PIEZOELECTRIC VOLTAGE SOURCE David B. Parkinson, Cleveland, Ohio, assignor to Clevite Corporation, a corporation of Ohio Continuation of application Ser. No. 541,784, Apr. 11, 1966. This application Dec. 23, 1968, Ser. No. 786,855 Int. Cl. H01v 7/00 US. Cl. 3108.3 2 Claims ABSTRACT OF THE DISCLOSURE This invention relates to a voltage source comprising a U-shaped frame member with a piezoelectric element located therebetween. An actuating device at the open end of the frame member for compressing the piezoelectric element. The actuating device is a camrning member on a rotatable shaft that is in contact with a cam follower that actually compresses the piezoelectric element as the camming member is rotated.

This is a continuation of application Ser. No. 541,79 filed Apr. 11, 1966, now abandoned.

This invention relates generally to an improved piezoelectric voltage source and, more particularly, to a piezoelectrically powered device utilizing a crankshaft-like actuator. The device being adapted to be employed as an igniter for gas fired products such as gas stoves, heaters, etc., and for other ignition purposes.

In the prior art the actuating mechanism for piezoelectric voltage sources has been essentially of the type utilizing sliding surfaces under pressure for transmitting the actuating force. It has been found that excessive friction prohibits the application of this approach to a device as shown herein. The present invention employs a structure which has an absolute minimum of compliance and thus is able to convert the mechanical energy into electrical energy much more etficiently. However this type of structure was prohibitive from ,a mechanical efficiency point of view when the teaching of the prior art was applied. It has now been found that the problem of excessive friction can be overcome by limiting all members of the actuating mechanism to a rolling surface contact.

[It is therefore the primary object of this invention to provide an improved piezoelectric voltage generator requiring comparatively low actuating force to produce a given voltage output.

It is a further object of this invention to provide a piezoelectric igniter in which the actuating mechanism has improved mechanical efficiency.

It is a still further object of this invention to provide a piezoelectric igniter in which the cooperating components of the actuating mechanism have only rolling contact.

An aspect of the present invention resides in the provision of a piezoelectric voltage source which includes a U-shaped frame member having in each leg an axially aligned opening. The piezolectric element is disposed between the legs and the element has a first and a second end face and a longitudinal axis which is normal thereto. The first end face' of the element bears against the closed end of the U-shaped frame. An eccentric cam mechanism is disposed in bearing relation to the second end face; this mechanism includes a crankshaft member which extends transversely acorss the legs and each end of the crankshaft is rotatably mounted in the aforesaid openings. The voltage source also includes an actuating member, such as a lever, connected to the crankshaft and is effective to rotate the same to cause the eccentric cam mechanism to move towards the closed 3,463,943 Patented Aug. 26, 1969 ice end of the U-shaped frame to compress the element to generate a voltage.

For a better understanding of the present invention, together with other and further objects thereof, reference is had to the following description taken in connection with the accompanying drawings, and its scope will be pointed out in the appended claims.

In the drawings:

FIGURE 1 is an exploded view of the piezoelectric voltage source in accordance with this invention;

FIGURE 2 is a front view of the assembled device shown in FIGURE 1; and

FIGURE 3 is a sectional view taken along lines 3-3 of FIGURE 2.

Referring now to the drawings there is shown a frame member 10 of generally U-shaped configuration having a closed end portion 12 with an irregularly shaped curvature. The other end of the U-shaped frame is open and defined by two legs 14, 16, each leg having an opening 18, 19, axially aligned with the other. The frame 10 is composed of steel or some other suitable metallic material which is essentially rigid against expansion when a force is applied thereto.

Disposed between the legs 14 and 16 is an assembly 17, composed of two piezoelectric elements 20, 22, but not limited thereto, which are arranged end to end in axial alignment with a metallic disc 24 interposed therebetween and encapsulated, except for the end faces, with silicon rubber. The elements are suitably electroded and poled to generate a voltage in response to a compression of the element in the direction of the longitudinal axis. The compression of the element in the manner as noted with generate a voltage of one polarity and the release of the compression will generate a voltage of opposite polarity. The elements are fabricated of a polycrystalline ceramic material such as barium titanate, lead titanate, zirconate or the like.

The elements 20, 22 are disposed mechanically in series and electrically in parallel establish a voltage at and through the center disc electrode 24.

The squeezing and actuating mechanism includes a generally cylindrical crankshaft 26 having intermediate to its axial ends a radially raised eccentric portion 28. Securely seated upon the eccentric portion 28 is a tubular needle bearing 30, the needle bearing in turn being adapted to receive a cam follower 32 having a peripherally located fiat spot 34. The crankshaft 26, together with the parts enumerated above, constitute the eccentric cam mechanism and this unit is extended transversely between the legs 14 and 16 and the axial ends thereof are received within the respective openings 18, 19. The axial ends of the crankshaft 26 are rotatably supported within the opening by means of a needle bearing 36 which is rigidly secured in each opening and adapted to receive the crankshaft 26. In view of the foregoing it will be appreciated that the crankshaft 26 may be rotated and that the cam follower 32 will move radially relative to the central axis of the crankshaft upon aforesaid rotation. One end of the crankshaft member 26 protrudes out of the opening 18 and is fixedly attached to an actuating lever 38.

As is illustrated in FIGURES 2 and 3, the flat spot 34 of the cam follower 32 bears against the end face of the piezoelectric element 22. The opposite end face of the assembly of piezoelectric elements is spaced relative to the closed end portion 12 of the frame 10 and abuts the flat face of a plate 40. The opposite face of plate 40 is rounded and bears against a wedge 42 suitably seated in the frame. The wedge 42 is formed of semicylindrical configuration and is seated in the end portion 12 of frame 10. All the members which are subof pre-compress'ion in the element, the axial end, faces' of the wedge 42 may be ground off to make the same flush with the surface of the frame member 10.

In the electrical circuit the plate 40 and the cam follower 32 serve-as the ground, Acable 44 is connected to the electrode 24. A spark gap is created between the made of hardened steelmai end-bf cable 44 and ground '(not shown) ,in suitable proximity to the combustible material to be ignited.

' In response to the application of a suitably directed force upon lever 38, the crankshaft is rotated causing the cam follower 32 to move towards and against the assemlily" of elements 17, compressing the elements 20, 22 against the wedge 42 and more particularly the 'end 12 of the frame member,;thereby generating a voltage output which can be taken from the'cable 44. The rounded surface of plate 40 facilitates an axial alignment of the force transmitted through the crankshaft 26 and elements 20, 22 toprevent fracture of the elements.

While there have been described what are at present considered to be the preferred embodiments of this invention, it will be obvious to those skilled in the art that various changes and modifications may be "made therein without departing from the invention, andit is aimed, therefore, in the appended claims to cover all such changes and modifications as fall within the true Spiritandscope of the invention.

What I claim is:

1. A piezoelectric voltage source, comprising:

a rigid U-shaped frame member having in each leg defining the open end thereof an axially aligned open- 8;

a 4 7 piezoelectric element rneans disposed parallel to and between said legs and having first and second axial end faces; said first end face bearing against the closed end of said U-shaped frame; cam means including a crankshaft extending'transversely across said legs and the ends thereof being rotatably mounted within the said opening, a circular sleeve eccentrically superimposed about said crankshaft intermediate to its axial ends; a cam follower having a cylindrical opening mounted about said circular sleeve fof relative rotation therebetween and a fiat portion in bearing relationship to said second endface; actuating means connected to said crankshaft and effective to rotate the latter to cause the 'cam follower to move axially towards the said closed end of said U-shaped frameand against said second end face to compress, said element means to generate a voltage. 2. A piezoelectric voltage source according to claim 1, and rolling contact bearings interposed between said sleeve and said cam follower.

References Cited UNITED STATES PATENTS 3,101,420 Hufferd 310-8] 3,114,059 12/1963 Hulferd- 310-91 3,208,443 9/1965 Hurwitz 123-148 3,211,069 10/1965 RiXtOn 95-115 3,211,949 10/1965 Slaymaker 315-55 3,350,608 10/1967 Maltner 3108.7 3,229,153 1/ 1966 Freeman 310-8 2,954,506 9/1960 Harkness 315-55 J. D. MILLER, Primary Examiner US. Cl. X.R. 

